The use of printed identification tags to code information that can be sensed by optic sensors is well known. Numerous tags have been designed for a number of different applications. Probably the most common of which is the bar code as used, for example, in grocery stores to identify packaged items.
It is also known to apply tags with specific coded information thereon and to use this coded information to control the movements of the coded article in accordance with the information coded on the tags, for example, this process is used to identify railway cars and sort them and is also used at some airports, for example, to direct luggage to its correct destination.
The tags may take any suitable form but it is essential that the tag reader be able to a) locate the tag in the image b) orient the tag in the image (assuming that it is randomly applied) and c) decode the tage which obviously requires a) and b) be performed. This process is made considerably more reliable when the perimeter or a reference perimeter of the tag is easily identified.
It is also important to permit as much information as possible to be coded into the space available on the tag.
One of the more common forms of the tag utilizes an array of cells set up in mutually perpendicular rows and columns and wherein the information is coded in each cell by one of a selected pair of contrasting colours, for example, black and white, so that the tag reader can then easily discriminate one type of cell from another and by using the binary system clearly identify what is coded therein.
U.S. Pat. No. 4,924,078 issued May 8, 1990 to Anselmo et al discloses a matrix type arrangement having internal data field surrounded by a border and an external data field around the border (the external data field may be eliminated if desired), while U.S. Pat. No. 4,939,354 issued Jul. 3, 1990 to Priddy discloses another machine readable binary coded tag format.